Technical Abstract:
Airborne dust is often emitted from bare, loose soil and road surfaces during intense wind events. Little is currently known about the amount and physical characteristics of the dust and their relation to properties of the source area. We sampled wind-erodible sediment from 76 sites including agricultural soils, sand dunes, playa surfaces, and unpaved roads in the Southern High Plains in west Texas and east New Mexico, USA. Dust was created by agitating 400 g of air-dried samples under controlled laboratory conditions using a rotating cylinder dust generator. Airborne dust par- ticle size distributions were measured in situ by laser diffraction after 2 and 4.5 minutes of sample agitation. Analyses of the effect of time of agitation indicated the fraction of particles 2.5, 10, and 25 microns significantly increased with time of agitation. The airborne dust distributions were mathematically described using a Weibull distribution of fthe form: Fraction of particles of size x or smaller = 1 - EXP(-((Particle size x/B)**C)) where B and C are equation parameters. Correlations of pre- dicted particle sizes with more than 5000 observations made with the laser particle diffractometer had a coefficient of determination of 0.93. Mean particle concentrations of the airborne dust (mg m-3), for particles with an aerodynamic diameter less than or equal to 10 microns (PM10), were measured after each 4.5 minute run. Analyses of variance indicated PM10 concentrations were significantly correlated (P less than or equal to 0.05) with source location. The concentration of airborne dust generated by soil or roadside drainage ditch sources was about one-half that generated by unpaved road sources.